If a fault occurs in the air-mass sensor signal of the air-mass sensor, known operating methods have the disadvantage that the control/regulation of the internal combustion engine is influenced in such a way that the internal combustion engine will no longer operate at the optimal operating point.
When driving on a wet surface, for instance, spray water may get into an intake tract of the internal combustion engine, where it can penetrate an air filter and wet an air-mass sensor installed in the intake tract. This effect, which is also known as water entry, is particularly disadvantageous for the widely used hot-film air-mass sensors, which have a heating surface that cools when brought into contact with water in the liquid phase, with the result that the air-mass sensor signal generated by the air-mass sensor is distorted.
Using the distorted air-mass sensor signal, the control unit controlling/regulating the internal combustion engine calculates an incorrect value for the air-fuel ratio to be set, so that the internal combustion engine no longer operates at the optimal operating point.
Furthermore, the emission values of the internal combustion engine are affected by water entry, since a portion of the introduced water or the water vapor generated therefrom reaches a combustion chamber of the internal combustion engine, where it displaces a portion of the air quantity required for combustion.
Accordingly, it is an object of the present invention to provide a method for operating an internal combustion engine that minimizes the influence of an interference variable, which affects the air-mass sensor signal, and in turn effects the regulation of the internal combustion engine.